174- 



PELVIS. 



TABLE OF COMPARATIVE PELVIC ANGLES. 



Having thus taken a general review of the 

 progressive development of the pelvis, and 

 traced it from its most perfect form in man 

 to its most rudimentary elements in the fishes; 

 we can enter more prepared into the consi- 

 deration of the serial homologics of the pelvis 

 and its ligaments. 



SERIAL HOMOLOGIES OF THE PELVIC BONES 

 AND LIGAMENTS. 



The sacrum, according to Professor Owen, 

 is to be considered as the centrum of the pelvic 

 vertebral elements. The ankylosed bodies of 

 the sacral vertebrae, as well as their coalesced 

 laminae, spinous and articular processes, are 



sufficiently evident as the representatives of 

 those components of the neural arch in the 

 typical vertebra.* The lateral masses of the 

 sacrum which support the ilia are, however, 

 made up of two elements coalesced together, 

 as is shown in the manner of their develop- 

 ment, before described, viz., first, of the true 

 transverse processes, or " diapophyset" con- 

 stituting the external row of tubercles seen on 

 the posterior surface of the sacrum, and which 

 are ossified, like those of the true vertebrae, by 

 extension from the same points of ossification 

 as the laminae, and spinous and articular pro- 

 cesses ; and, secondly, of the six characteristic 

 sacral ossific points, three on each side of the 

 three upper sacral bodies, which are placed on 

 the anterior surface of and below the former, 

 between the sacral foramina, as before de- 

 scribed. 



These ossific points, as shown in prepara- 

 tions exhibited to the British Association, in 

 1837, by Mr. Carlyle, were four in number 

 on each side, and very distinct from the true 

 transverse processes ; and they were con- 

 sidered by him to represent the necks and 

 heads of four sacral ribs on each side. Upon 

 the truncated extremities of these three or 

 four sacral ribs the auricular facets are sup- 

 ported. They appear to be similar to the 

 anterior roots of the cervical transverse pro- 

 cesses, upon the last of which is occasionally 

 developed, in the human subject, a short costal 

 process. In the nomenclature of Professor 

 Owen, they may be considered the sacral " pa- 

 rapophyses" but differ from these processes as 

 seen in the rib-bearing vertebrae of the Croco- 

 dile, in being developed by separate and distinct 

 centres. Blainville remarks that the four upper 

 sacral vertebras, scientifically considered, com- 

 pose the whole of the true sacral elements ; and 

 that the fifth, which he calls " subsacral" is an 

 ankylosed coccygeal vertebra. But the lateral 

 epiphysial plates of bone before described 

 the upper of which forms the auricular facet, 

 opposite the three first, and the lower, the 

 sides of the two last sacral vertebrae would 

 seem to connect these vertebrae more particu- 

 larly together, and to be the coales< <;d serial 

 homologues of the epiphyses forming the ar- 

 ticular facets on the tubercles of the ribs. In 

 the Saurian reptiles these sacral ribs, two in 

 number on each side, are very distinctly 

 analysed, and have been before mentioned as 

 intervening between the sacrum and the ilia. 

 The anterior of these ribs in the Saurians are 

 said by Mr. Carlyle, to be articulated to the 

 bodies of the last dorsal and first sacral ver- 

 tebrae, as well as to the intervertebral sub- 

 stance between them'; and the posterior, to 

 the last sacral and first caudal vertebrae, and 

 to their intervertebral substance affording 

 an exact homologue to the true ribs. The 

 ilia in the human fcetus, and for some years 

 after birth, are connected to two only of the 

 sacral vertebrae ; but, in the adult state, they 



* A remarkable analogous instance of the coales- 

 cence of vertebrae to form one solid mass is seen in 

 those of the cervical region of the bottle-nosed 

 Whale. 



